Security printing is the field of the printing industry that deals with the printing of security documents such as banknotes, cheques, passports, tamper-evident labels, product authentication, stock certificates, postage stamps, identity cards, among other examples. A goal of security printing is to prevent forgery, tampering, or counterfeiting. Security printing can be done on commercial printers like traditional offset and flexographic presses, as well as using newer digital platforms. One security printing technique is sometimes referred to as split ink fountain or sometimes rainbow printing, by which security documents are produced, at least in part, by printing with more than one ink in a printing fountain to achieve a unique blended color/color pattern that is difficult to reproduce.